Utilização da espectroscopia no infravermelho próximo e quimiometria para diferenciação do tipo de cultivo de alfaces (Lactuca sativa) e couves (Brassica oleracea)

Abstract

In order to avoid fraud and that the term ”organic food”is misused, the development of nonexpensive, time-consuming and expensive methods of analysis is increasingly necessary. Near infrared reflectance spectroscopy (NIRS) is suggested as a possible alternative to the commonly used methodologies, as it is ideally capable of allowing fast, environmentally correct, nondestructive and non-invasive specimen distinctions. In this way, this work proposes a methodology for the differentiation of lettuces and cabbages cultivated conventional, domestic and organic through NIRS allied to the chemometric method of Principal Component Analysis (PCA). The Principal Component Analysis (PCA) method determines the combination of variables that describes the greatest variability of the data. The objective of this work was the use of Near Infrared Spectroscopy (NIR) associated to chemometric methods (PCA) for the construction of multivariate models of lettuce, differentiating the conventional ones from the organic ones. In the development of the study in the first part, 12 samples of conventional lettuces, 6 hydroponics and 6 organic, were analyzed in triplicate. The samples appeared to be very similar to each other, but the organic samples were significantly influenced by the vibrations of molecules composed of H2O, CH, CH2, CH3, ArOH, ROH, RNH2 , While the others were less influenced by these molecular vibrations. In the second part of the development of the work, a garden was built as close to organic as possible, using only organic compost of sheep, where it was planted cabbage-butter and crisp lettuce. For the sampling, 6 samples of conventional lettuces (AC), 6 of cultivated (ACULT), 9 samples of conventional cabbage (CC) and 6 cultivars (CCULT) were obtained, analyzed in triplicate. The region of greatest vibration was at 1400 - 1500 nm, being assigned to the samples of conventional, that region is characteristic of H2O, CH, CH2, CH3, ArOH, ROH, RNH2, ArCH and CONHR, again. The difference can be attributed to the influence that agricultural pesticides cause on these molecules. However, for this assertion, confirmatory chromatographic analyzes would be required. These results suggest that the proposed methodology can be an efficient tool for the sorting of organic lettuces.